Radial seal for rotary mechanism



Feb. 16, 1965 F. WANKEL 3,169,695

RADIAL SEAL FOR ROTARY MECHANISM Filed Dec. '7, 1962 3 Sheets-Sheet 1 INVENTOR. FzLix WANKEL Feb. 16, 1965 WANKEL RADIAL SEAL FOR ROTARY MECHANISM 3 Sheets-Sheet 2 Filed Dec. 7, 1962- INVENTOR. FELIX W/INKEL Feb. 16, 1965 F. WANKEL RADIAL SEAL FOR ROTARY MECHANISM 3 Sheets-Sheet 3 Filed Dec. 7, 1962 INVENTOR. FELI'X WANKEL United States Patent 3,169,695 RADIAL SEAL FOR RDTARY MECHANISM Felix Wankel, Lindau (Bodensee), Germany, assignor t0 NSU Motorenwerke Aktiengesellschaft, Neckarsulnm, Germany, and Wankel G.rn.b.H., Lindau (Bodensee), Germany Filed Dec. 7, 1962, Ser. No. 243,129 Claims priority, application Germany, Dec. 9, 1961,

N 20,9 12 Claims. (Cl. 230-145) This invention relates to a radial seal for rotary mechanisms such as rotary internal combustion engines, compressors, pumps and the like.

Rotary engines of this type generally comprise an outer body with axially spaced parallel end walls and a peripheral wall interconnecting the end walls and an inner body supported for relative rotation Within the outer body. One of said bodies has grooves extending over the whole axial width of the inner body and accommodates seal strips which are movable in a direction towards the peripheral wall of the other body and serve to seal adjacent working chambers from each other. In known constructions, said seal strips which can be arranged either within the inner body or rotor or within the outer body or housing, are urged against the peripheral wall of the other body i.e. against the inner surface of the housing peripheral wall or towards the outer peripheral wall or outer surface of the rotor, substantially by the gas pressure existing in one of the adjacent working chambers. The pressure gas can enter the grooves accommodating the seal strips and acts on the bottom surface of the seal strips to urge them against the peripheral wall. This results in a comparatively high frictional force between the outer edge of the seal strip and the peripheral wall and this frictional force tends to rock the seal strip about an outer edge of its groove. In almost all types of rotary engines the seal strip performs a tilting movement with respect to the peripheral wall and such rocking motion can cause a jamming of the seal strip within its groove thus preventing free radial movement of the seal strip with consequent high wear of the edge of the seal strip and the risk of damaging the peripheral wall.

It is the primary object of the present invention to keep the seal strip free of the frictional forces generated between the edge of the seal strip and the peripheral wall. According to the invention a shoe is arranged between each seal strip and the peripheral wall. The shoe extends over the whole length of the seal strip and comprises a sliding surface for sliding along the peripheral wall. It is anchored within the body which accommodates the seal strip for tilting or pivotal motion about an axis parallel to the rotational axis of the inner body and the upper and lower surfaces of the shoe are exposed to the gas pressure existing within the adjacent working chamber. By this arrangement, the frictional force is taken up by the shoe and, therefore, can not cause a rocking of the seal strip within its groove. Owing to the pivotal anchoring of the shoe the mobility of the seal strip towards the peripheral wall under action of the gas pressure is not impaired. The radial seal of the present invention operates in generally the same manner as the usual seals in which the seal strip is directly in contact with the peripheral wall. Thus the engagement of the sliding surface of the shoe with the peripheral wall is effected by the pressure gas entering the groove accommodating the seal strip. Consequently, the radial seal with the peripheral wall is effected, as heretofore, by the force acting on the seal strip. Naturally a spring can be located underneath the seal strip to obtain the necessary contact pressure if there is no gas-pressure.

Preferably the shoe is arranged in such a way that it is trailed or dragged with respect to the direction of ro- 3,ih,695 Patented Feb. 16, 1965 tation of the inner body relative to the outer body in order to prevent the shoe from spreading between its anchorage and the peripheral wall. The shoe can be made of a flexible material such as spring steel and in this case the shoe need not be hinged to the body as, due to its inherent flexibility, the shoe permits movement of the seal strip.

Preferably the shoe is arranged substantially parallel to the peripheral wall of the body accommodating the shoe so that only small tilting motions about its axis are necessary to keep the shoe in contact with the peripheral wall.

The direction of movement of the seal strip is preferably substantially perpendicular to a straight line interconnecting the tilting axis of the shoe with the contact point between the shoe and the seal strip. By this arrangement, the forces that cause a tilting movement of the shoe in a radial direction act in the direction of movement of the seal strip consequently do not exert any forces that tend to rock the seal strip within its groove. Any tendency to thus rock the seal strip can be further minimized by having the contact surface between the shoe and the seal strip made spherical.

Furthermore the shoe can be made of several parts with one of said parts carrying the sliding surface and being preferably hinged to the other part that is tiltably anchored within the body. By this arrangement, the contact area between the sliding surface and the peripheral wall can be enlarged as the part carrying the sliding surface can tilt to adapt itself to the surface of the peripheral wall. In this way the pressure per unit of contact area between the sliding surface and the peripheral wall is decreased. A hinged connection between both of said parts is not necessary if the part anchored in the body is made of a flexible material such as spring steel as in this case the flexibility of this part permits the part carrying the sliding surface to perform the necessary tilting movement.

Several embodiments of the invention used in connection with a rotary internal combustion engine having the radial seals arranged within the inner body or rotor are shown in the accompanying drawings, in which:

FIG. 1 is a side view of a rotary internal combustion engine with one of the Walls removed so as to show the arrangement of the rotor in the housing and with portions illustrated in section so as to show the ports and the ignition means;

FIG. 2 is a detailed, enlarged view of the apex of the rotor showing the arrangement of the sealing strip and shoe;

FIG. 3 is a view in the direction of the arrows on the line 3-3 of FIG. 2;

FIGS. 4, 5, and 6 are detailed side sectional views of the apex portions of the rotors showing three modified arrangements of sealing strips and shoes;

6 FIG. 7 is a perspective view of the shoe shown in FIG.

; and

FIGS. 8 and 9 are side elevational and perspective views respectively of the apex portions of rotors showing two further modified forms of sealing strips and shoes.

With reference to FIGS. 1 to 3 the rotary internal combustion engine comprises a housing having two axially spaced parallel end walls 1 and 2 and a peripheral wall 3 arranged therebetween. The inner surface 4 of the peripheral wall 3 preferably has the shape of a twolobed epitrochoid. A shaft 6 is journaled in the housing, said shaft having an eccentric portion 8 on which a three-pointed inner body or rotor It) is journaled. The apices 12 of the rotor 19 slide along the inner peripheral surface 4 thereby forming three variable volume working chambers A, B, C. The rotation of the rotor it is in direction of the arrow D. Gearing (not shown) ensures a certain speed ratio between rotor 10 and shaft 6, said speed ratio being 1:3 .in the embodiment shown. The

' peripheral wall 3 is provided with an intake port 14, ignition means such as spark plug 16 and an outlet 'port if? whereby a complete four-stroke cycle canbe per- "tanned within'each working chamber. In the position of the rotor shown in PEG. 1, working chamber A per forms the intake stroke, working chamberB ,performs the compression stroke and working chamber C performs theexhaust stroke; V j

-lFor efiectiv operation of the engine. the Workingchamersjniistgb sealed. For this purpose each rotor apex 12 carries a radial seal generally designated 2% in FIG. 1 for sealing engagement withthe inner peripheral wall 4. For sealing between the end faces. of rotor and the end Y walls of the housing each rotor end face carries axial fseals that consist of axially movable seal strips 22 extendmg between adjacent rotor 'apices 12 and being in sealing engagement with the radial seals 2% by way'of'axially mov able intermediatese'al bodies 24.

The const'ni ctioh of the radial seals 2b is shown in detail in FIGS; 2 and 3. Each rotor apex 12 has a groove firs eriteiidi'n'g over the-whole axial width as the rotor and accommodating a seal strip 28 that is movable in a direction towards the inner peripheral wall 4. A spring 46.

with the peripheral Wall 4 is designated 38 and the contact spot of the seal strip 28 with the shoe 30 is designated 40; The shoe 3tlis arranged in trailing relation with re- 'spect to the direction of rotation D of. rotor 10 and its end .44 is pivotally or tiltably anchored within a recess 34 about an axis parallel to the turning axis M of the rotor 19. In

the position shown in FIG. 2 this axis is formed by the edge 36 of recess 34. An abutment 42 of rotor 10 that overlaps the end 44 of shoe 3t! prevents the ejection ofthe shoe frornthe recess 34, under centrifugal force. On assembly, the end 44 is inserted laterally into the recess 34 and is, therefore, axially movable with respect to the rotor 10. Because of this, on axial displacementof the rotor, no axial guidance of the rotor is performed by the shoes. In FIG. 2 it is assumed that the higher pressure is withinworking chamber C; This pressure acts on the upper surface of the shoe 3% and, therefore, tends to urge the sliding surface 32 away from the inner peripheral wall 4. In order to prevent this; means are provided to ensure that the gas pressure can act also on the bottom surface of shoe 30, for instance by having the lateral edges 31 of -Sl'10e 30 tapered as shown in FIG. 3 so that pressure gas can stream underneath the shoe 30 through the wedgeshaped gaps between the edges 31 and the adjacent end walls 1,- 2 of the housing. This pressure gas balances the pressure gas acting on the upper surface of the shoe. The pressure gas flows into groove 26 beside and underneath the seal strip 28 and urges the strip against the opposite wall of groove 2s and in conjunction with spring 46 urgesit against shoe 30 which thereby is pressed against the-inner peripheral wall4. It is likewise possible to provide a separate spring acting directly on shoe 3%, such spring 61 being shown in dotted lines in FIG. 2.

In order to ensure contact of the sliding surface 32 with the inner peripheral wall 4 under the gas pressure generated in" the rotary engine certain dimensions have to be maintained. Referring to FIG. 2, if a represents the area determined by the distance between the contact points 38 and 40, and b represents the area determined by thehalf .of therseal strip 28, and 0 represents the moment arm with respect to the tilting axis 36 of the gas pressure acting on area tr, .landfd represents The moment arm with respect to -4. .1 tilting axis 36 ofthe gas pressure acting on area b, the product of a and. c must be smaller than the product of b and d in order to maintain the sho e in contact with the inner peripheral surface 4-.

Instead of and in addition to the tapered edges 31, the

shoe 30 can also be provided withopenings 48 shown in FIG. 3 in'dottedzline. These openings 48 have the additional advantage thatthe heat-absorbing surface of the shoe is decreased. V V v The directionQof movement of seal strip28 generally is perpendicular .to the straight line interconnecting the tilting axis 36 of shoe3l) with the contact spot 40 between the shoe and the seal strip'28. -.Therefore,' the forces that. a tend to tilt the shoe 3% radially towards the inner peripheral surface .4,.can act substantially in a radial direction of movement" of the seal strip only and cannot cause a rocking of the seal strip withinits groove 26. This can be favoredin the manner indicatedin FIG. 4 by providing acontact area 50 of shoe-.391" with a spherical shape as shown in FIG. 4. ,In this embodiment the seal strip 28" 7 does not project out of groove 26. Spherical contact area St) engagesthe outer end-of seal strip 28" near the outer end of the groove; The apex portion of rotor 19 may be modified in profile so that thelefthand portion thereof as viewed in FIG. 4' projects to the outer end of the groove.

If ithe'higher gas pressure is within working chamber B, the seal strip 28 or 28" is urged againstthe opposite wall of-the groove and the pressure gasentering groove 26 can act on the bottom surface of the seal strip 28 or 28" thereby'urging seal strip 28 or 28" against the .shoe'30- or 30" and shoe 3% or 30 with its sliding surface 32 against the inner peripheral Wall 4. The gas pressure also acts on the front face of shoe 36 or 30' and tends to'shift the shoe 3.0 or 30'" to .theright against the action of the frictional forces. Thisis possible until the end 440i shoe 30 and 30' abuts againstwall 52 of recess 34. The wall 52 formsa corner 54 that covacts with theacute end 44 of the shoe. Thiscorner 54, therefore, forms in thiscase .the tilting axis for shoe 30. i i

In the embodiment of FIG. Sthe anchoring of shoe 3% is effected by screwsi that project through bores 58 of shoe 30. These bores have adiarneter larger than the diameter of the screws 56 and, therefore, enable the necessary tilting movement of shoe 30.

In the embodiment of FIGS. 6 and the shoe 30" is made of a flexible material e.g. spring steel and one of its ends is fixed to the inner body 10; For this purpose this end of the. shoe is slotted to form lugs 60, 62 that are bent at different angles. The lugs are inserted laterally in correspondinggrooves:64, 66 within the inner body 10. The

different angles prevent theshoe from being pushed (out of its anchorage e.g. by centrifugal forces} Owing to its flexibility the shoe 30 can perform the necessary tilting movements to have its sliding surfacein continuous contact withthe inner'peripheralwall'4; Preferably the shoe is formed in such arnanner that it has an'initial tension towards the inner peripheral wall. The sliding surface 32" can be made of another material that has better antifriction; properties than spring steel. Naturally the shoe 30" can also be fastened byother means to'the rotor 19,

eg. by screws.

'The embodiment of FIG. 8 differs from that one of FIGS; 6 and 7 only by the fact that the sliding surface is formed by a separate part 65 which is connected to a second part 67 made offlexible material and fastened to the inner body 10 in the same manner as the shoe 39" in FIG.

6. The sliding surface has two crestsqGS that areparallel to the axis of-ro-tation of rotor wand that slide along the inner pcripheral'wall 4. Owing to the flexibility of part 67,"the part ,GS-can-tilt relative to the rotor in such this purpose part 65 has a groove 70 circular in cross section for accommodating the correspondingly shaped end 72 of part 67'. The other end '74 of part 67' is also circular in cross section and engages the corresponding groove 76 of inner body 10. Naturally other hinge connections could also be used.

Thus it will be seen I have provided an improved radial seal for rotary mechanisms in which the seal is free of any frictional forces and which will provide adequate sealing between the working chambers over a long period of time with comparative freedom from wear. Modifications may be made in the illustrated and described embodiments of my invention without departing from the invention as set forth in the accompanying claims.

I claim:

1. A rotary mechanism having an improved radial seal comprising an outer body having axially spaced parallel end Walls, a peripheral wall interconnecting the end walls and an inner body mounted within the outer body for rotation relative to the outer body, said inner body having a plurality of circumferentially spaced grooves extending over the whole axial width of the inner body, seal strips mounted in said grooves and extending between the end walls of the outer body and movable in a direction towards the peripheral Wall of the outer body, and a shoe arranged between each seal strip and the peripheral wall, said shoe including a head portion and a body portion with the head portion extending over the whole axial length of said seal strip and having a radially outer surface for sliding along the peripheral wall and a radially inner surface for engagement with said seal strip thereby to provide adjacent chambers on opposite sides of said shoe, said chambers being sealed from each other by the engagement of the radially outer surface of the head portion of said shoe with the peripheral Wall and the engagement of the radially inner surface of the head portion of the shoe with said seal strip, the body portion of the shoe being anchored within the inner body for tilting motion of the shoe about an axis parallel to the rotational axis of the inner body, and with the radially outer surface exposed to the gas pressure of the adjacent working chamber, and said body portion being formed to provide a gas passage between the radially inner and outer surfaces thereof whereby the gas pressure on the two radial surfaces is equalized.

2. A rotary mechanism as claimed in claim 1 in which the body portion of said shoe is mounted adjacent its leading edge and the head portion of said shoe is in trailing relation with respect to the direction of rotation of the inner body relative to the outer body.

3. A rotary mechanism as claimed in claim 1 in which the body portion of said shoe is inserted in a recess formed in the inner body.

4. A rotary mechanism as claimed in claim 1 in which the shoe is made of a flexible material.

5. A rotary mechanism as claimed in claim 1 in which the direction of movement of the seal strip is substantially perpendicular to the straight line interconnecting the tilting axis of the shoe with the contact point between the radially inner surface of the head portion of said shoe and the seal strip.

6. A rotary mechanism as claimed in claim 1 in which a spherical contact surface is provided between the head portion of said shoe and seal strip.

7. A rotary mechanism as set forth in claim 1 in which the head portion of said sliding surface of the shoe is kept in contact with the peripheral wall by the forces acting on the seal strip.

8. A rotary mechanism as set forth in claim 1 in which a spring is provided to urge the shoe against the peripheral wall.

9. A rotary mechanism as set forth in cl-aim 1 in which the shoe is substantially parallel to the peripheral wall of the body accommodating the shoe.

10. A rotary mechanism as set forth in claim 1 in which the shoe is made of several parts, one of said parts forming the head portion and the other part forming the body portion and being anchored to said inner body and both parts bflilng connected for tilting movement with respect to each 0 er.

11. A rotary mechanism as set forth in claim 1 in which the sliding surface of the head portion of said shoe comprises two crests that are parallel to the rotational axis of the inner body and slide along the peripheral wall.

12. A rotary mechanism having an improved radial seal comprising an outer body having axially spaced parallel end walls and a peripheral wall interconnecting the end walls, and an inner body mounted within the outer body for rotation relative to the outer body, one of said bodies having a plurality of circumferentially spaced grooves extending over the whole axial width of the inner body, seal strips mounted in said grooves and movable in a direction towards the peripheral wall of the other body, a shoe arranged between each seal strip and the peripheral wall, said shoe extending over the whole axial length of said seal strip and comprising a sliding surface for sliding along the peripheral wall to thereby provide adjacent chambers on opposite sides of said shoe, said chambers being sealed from each other by the engagement of the shoe with the peripheral Wall and the engagement of the shoe with said seal strip, said shoe Ibeing anchored within that body accommodating the seal strip for tilting motion about an axis parallel to the rotational axis of the inner body, the radially outer surface and the radially inner surface of the shoe being exposed to the gas pressure existing within the adjacent working chamber.

References Cited by the Examiner UNITED STATES PATENTS 49,070 8/65 Biclcford 91-149 84,280 11/68 Kaiser 103-140 105,796 7/70 Fuller 103-140 501,864 7/93 Boening et al 103-140 803,406 10/05 Davis 91-149 1,033,748 7/12 Standish 123-17 1,453,683 5/23 Kochendarfer 91-149 2,135,760 9/35 Moore 103-140 JOSEPH H. BRANSON, 1a., Primary Examiner. WILBUR J. GOODLIN, Examiner. 

1. A ROTARY MECHANISM HAVING AN IMPROVED RADIAL SEAL COMPRISING AN OUTER BODY HAVING AXIALLY SPACED PARALLEL END WALLS, A PERIPHERAL WALL INTERCONNECTING THE END WALLS AND AN INNER BODY MOUNTED WITHIN THE OUTER BODY FOR ROTATION RELATIVE TO THE OUTER BODY, SAID INNER BODY HAVING A PLURALITY OF CIRCUMFERENTIALLY SPACED GROOVES EXTENDING OVER THE WHOLE AXIAL WIDTH OF THE INNER BODY, SEAL STRIPS MOUNTED IN SAID GROOVES AND EXTENDING BETWEEN THE END WALLS OF THE OUTER BODY AND MOVABLE IN A DIRECTION TOWARDS THE PERIPHERAL WALL OF THE OUTER BODY, AND A SHOE ARRANGED BETWEEN EACH SEAL STRIP AND THE PERIPHERAL WALL, SAID SHOE INCLUDING A HEAD PORTION AND A BODY PORTION WITH THE HEAD PORTION EXTENDING OVER THE WHOLE AXIAL LENGTH OF SAID SEAL STRIP AND HAVING A RADIALLY OUTER SURFACE FOR SLIDING ALONG THE PERIPHERAL WALL AND A RADIALLY INNER SURFACE FOR ENGAGEMENT WITH SAID SEAL STRIP THEREBY TO PROVIDE ADJACENT CHAMBERS ON OPPOSITE SIDES OF SAID SHOE, SAID CHAMBERS BEING SEALED FROM EACH OTHER BY THE ENGAGEMENT OF THE RADIALLY OUTER SURFACE OF THE HEAD PORTION OF SAID SHOE WITH THE PERIPHERAL WALL AND THE ENGAGEMENT OF THE RADIALLY INNER SURFACE OF THE HEAD PORTION OF THE SHOE WITH SAID SEAL STRIP, THE BODY PORTION OF THE SHOE BEING ANCHORED WITHIN THE INNER BODY FOR TILTING MOTION OF THE SHOE ABOUT AN AXIS PARALLEL TO THE ROTATIONAL AXIS OF THE INNER BODY, AND WITH THE RADIALLY OUTER SURFACE EXPOSED TO THE GAS PRESSURE OF THE ADJACENT WORKING CHAMBER, AND SAID BODY PORTION BEING FORMED TO PROVIDE A GAS PASSAGE BETWEEN THE RADIALLY INNER AND OUTER SURFACES THEREOF WHEREBY THE GAS PRESSURE ON THE TWO RADIAL SURFACES IS EQUALIZED. 